1. Paediatric Research Group, M.R.C. Clinical Research Centre, Watford Road, Harrow Middx. HA1 3UJ, U.K.
2. Division of Pediatric Metabolism, Duke University Medical Center, Durham, NC 27710, U.S.A.
3. Veterans' Administration Medical Center, Departments of Pharmacology and Medicine, Case Western Reserve University School of Medicine, Cleveland, OH 44106, U.S.A.